The Marvel universe is one of the most populous and diverse universes in comic books and as well as movies. There is no shortage of alien races (friendly and hostile) who have their own version of superheroes and supervillains. They may not be as clear as Earth, however, let’s face it; humans are simply weaker than other alien races in the Marvel universe.
The Earth is really at the mercy of the Avengers and powerful alien races, who fortunately do not see humans as slaves. There are some alien beings in the Marvel universe that make us look like bacteria, by comparison, FIVE of them reminding humans not to be overly enthusiastic here.
They are the nemesis alien race of the Skrulls. The two wage perpetual wars against each other from time to time; nevertheless, it is the Kree that dominates the military and the technology. They also love to engage in some genetic experiments and were responsible for creating Inhumans.
In addition to that, they also know how to create their own Ultron version without failing the same way humans do. Kree has been successful in inventing giant autonomous robots called Kree Sentry that can last for thousands of years and can also fight for them. Last but definitely not the least, they have Ronan the Accuser and Mar-Vel (the man responsible for making Carol Danvers Captain Marvel).
If you live in an extra-dimensional pocket of the universe from all the wars of the Kree, the Skrulls and the Shi’ar, you certainly don’t want anything else. It radiates the Asgardians (humanoid divine “aliens“). However, despite Asgard’s beautiful sunny paradise, they aren’t afraid when it comes to protecting his house.
They have the biggest heavy-hitters in Marvel. To name a few Thor, Odin, Hela, Loki, etc., and have different modes of travel around. Against the Shi’ar, it is a real close fight, but the Asgardians might eventually end up winning. They are multi-dimensional mini-gods fighting the traditional alien race.
One of the oldest alien races ever- which just wants to record stuff.
The Watchers prefers in staying true to their name, they watch. They use tremendous power through the knowledge of their universe but refrain from using it for their own benefit. It’s not fair to judge them against races that have their own military and technological powers, but the Watchers deserve to be at the top of the list for their strength and defiance against the Celestial.
Being immortal, there really isn’t much to do besides their hobbies.
One of them, the Ego, likes to create stuff (depicted as Planetary Celestial in Guardians of the Galaxy Volume 2), and the other, the Grandmaster just loves to create games for humans. Each elder respects the other and treats other elders as brothers or sisters, yet they do not associate with one another.
They stand among the oldest and most powerful beings in the universe and their creator, FIRST FIRMAMENT, they can create life. They can also create death, and some people want to toy with life. This angered the FIRST FIRMAMENT and led to a war between loyal Celestials (called Aspirants) and rebels. The First Firmament and Aspirants lost and fled to another reality.
It left Celestials to do as they please. And they chose to interfere with human life and caused all sorts of evolutionary and cosmic changes there, giving birth to superheroes and mutants. Oh, they are also immortal, and their cosmic powers are vast and beyond measure – perhaps without limitations.
Celestials can be as powerful as they are still made of a little bit of organic matter (they have skulls and brains), meaning they are physical beings. That means they can still be defeated and most of them have been in Marvel Comics. Infinites, on the other hand, are abstract beings; they also use incalculable power and can easily move through several multiverses.
Their name describes what they are. They don’t exist in the multiverse. They come from the outer dimension of the multiverse and are close to the Almighty. For that matter, no one has seen Beyonders. These aliens send their agents to deal with the denizens of the multiverse. To give you an idea of their vastness, they can collect planets as trinkets.
Beyonders like to experiment and toy with the multiverse, just like an aquarium. At one point, they even managed to kill all the Celestials with other abstract beings, such as Eternity and Infinity, only for the sake of experimentation.
They are not invincible still; Doctor Doom was able to steal the power of a Beyonder and literally become a God of Multiverse. Still, there is no doubt that they are the most powerful alien race in Marvel.